Design of XS (X = W or Mo)-Decorated VS Hybrid Nano-Architectures with Abundant Active Edge Sites for High-Rate Asymmetric Supercapacitors and Hydrogen Evolution Reactions.

Two-dimensional layered transition metal dichalcogenides have emerged as promising materials for supercapacitors and hydrogen evolution reaction (HER) applications. Herein, the molybdenum sulfide (MoS )@vanadium sulfide (VS ) and tungsten sulfide (WS )@VS  hybrid nano-architectures prepared via a facile one-step hydrothermal approach is reported. Hierarchical hybrids lead to rich exposed active edge sites, tuned porous nanopetals-decorated morphologies, and high intrinsic activity owing to the strong interfacial interaction between the two materials. Fabricated supercapacitors using MoS @VS  and WS @VS  electrodes exhibit high specific capacitances of 513 and 615 F g , respectively, at an applied current of 2.5 A g  by the three-electrode configuration. The asymmetric device fabricated using WS @VS  electrode exhibits a high specific capacitance of 222 F g  at an applied current of 2.5 A g  with the specific energy of 52 Wh kg  at a specific power of 1 kW kg . For HER, the WS @VS  catalyst shows noble characteristics with an overpotential of 56 mV to yield 10 mA cm , a Tafel slope of 39 mV dec , and an exchange current density of 1.73 mA cm . In addition, density functional theory calculations are used to evaluate the durable heterostructure formation and adsorption of hydrogen atom on the various accessible sites of MoS @VS  and WS @VS  heterostructures.